All over the world, an LTE mobile communication system is commercialized to provide a service.
In LTE, an HARQ and an ARQ are independently operated in order to recover an error which occurs when a terminal and a base station transmit data. The HARQ operates in an N-process stop-and-wait ARQ scheme. When a transmitter side receives a feed-back representing that the transmitter side transmits data with respect to one HARQ process and normally receives data from a receiver side (HARQ ACK), the transmitter side transmits next data. Otherwise, when the transmitter side receives a feed-back that an error occurs in the data received from the receiver side (HARQ NACK), the transmitter side re-transmits the corresponding data. The HARQ is used by defining the maximum number of transmission times. When the error continuously occurs for the maximum number of HARQ transmission times or when the feed-back is the HARQ-NACK, but an NACK-to-ACK error occurs, and as a result, when the HARQ NACK feed-back is mis-interpreted as HARQ ACK feed-back, data is lost.
When the data loss exerts a fatal influence on performance like TCP application, the data loss is recovered through ARQ retransmission in order to reduce a data loss ratio. The ARQ retransmission operates in a selective repeat ARQ scheme. In general, the receiver side starts a timer when the data loss is detected. A timer value is set to a time considering the maximum number of HARQ transmission times to recover the data loss through the HARQ retransmission. When the timer expires, the receiver side may report data receiving status information to the transmitter side and the status information includes lost data information, and as a result, the transmitter side may retransmit only the lost data.
In the LTE, the HARQ and the ARQ operate independently from each other, and as a result, the ARQ retransmission is performed later than the time of the data loss due to the timer value set to the time considering the maximum number of HARQ transmission times and a time when the receiver side transmits the data receiving status information to the transmitter side.